Question

A silver article generally turns black when kept in open for a few days. The article when rubbed with toothpaste again starts shining.
i. Why do silver articles turn black when kept in the open for a few days? Name the phenomenon involved.
ii. Name the black substance formed and give its chemical formula.

Answer 1

i. Silver reacts with hydrogen sulphide gas present in air and forms a compound Ag2S. This compound is black in colour. Hence, silver articles turn black when kept in the open for a few days. This phenomenon is called corrosion.
ii. The black substance formed issilver sulphide. Its chemical formula is Ag2S.